The goal of this study is to evaluate a group-based motivational interviewing (MI)-delivered risk reduction program for homeless young adults. It is hypothesized that youth who participate in the program will show greater reductions in substance use intentions, behavior and consequences, as well as sexual activity intentions and risk behavior, over a 3-month period compared to a usual care control sample of youth who do not participate in the program.

This study addresses an important gap in prevention services for homeless youth by conducting a pilot test of an innovative 4-session integrated substance use and sexual risk reduction program for this population that is feasible to deliver in settings where these youth seek services. The study has 2 specific aims:

Aim 1: Investigate whether homeless youth who participate in the program show reductions in substance use and intentions, behavior and consequences, as well as sexual activity intentions and risk behavior, over a 3-month period compared to a usual care control sample of youth who do not receive the program.

Aim 2: Gain a better understanding of intervention effects by exploring whether improvements in self-efficacy, readiness to change, outcome expectancies, and exposure to peer substance use and offers serve as explanatory mechanisms for reductions in substance use- and sexual activity- related intentions and risk behaviors among youth who participate in the program.

The program will be evaluated using a form of group-randomized design, although with crossover of conditions and groups to avoid the problems of power reduction associated with conventional group randomization. The unit of analysis will be the individual, but individuals will be assigned to groups based on the agency where they are seeking services. Youth at two drop-in centers serving homeless youth will either be in the intervention condition or a "usual care" control condition. The field period will be divided into four phases. The two agencies will alternate across phases in serving as the "intervention site" or "control site," with each agency having a total of two intervention phases and two control phases.

Intervention Condition: This condition involves a four-session voluntary intervention that is delivered within a drop-in center setting and is based on the investigator's previous intervention work with adolescents and young adults. Each session lasts approximately 1 hour. The intervention focuses on both sexual risk behavior and substance use. Although some sessions focus more heavily on sexual risk and others on substance use, each session includes content that emphasizes the interrelated nature of these two risk behaviors. In all sessions, participants will receive a personalized feedback sheet that specifically addresses a topic being discussed during that particular session. An motivational interviewing approach will be used to present material during the group sessions.

"Usual Care" Condition: The "usual care" condition reflects the resources typically available in settings that serve homeless youth: an HIV informational brochure that discusses the connection between substance use and HIV risk, and a Community Resource Guide that lists free or low-cost substance use and HIV-related services.

Inclusion Criteria:

• between 18-24 years, receiving services at one of the participating drop-in centers, planning to be in the study area for the next month

Exclusion Criteria:

• obvious cognitive impairment observed during screening process; non-English speaking